Synthesis and Structural Characterization of a Uranyl(VI) Complex Possessing Unsupported Unidentate Thiolate Ligands

Abstract

The synthesis and structural characterization of the first example of a uranyl(VI) complex possessing unsupported unidentate thiolate ligands, UO2(S-2,6-Cl2C6H3)2L2 (2b, L=N,N-diisobutylisopropylamide), are reported. Isolation of 2b as a stable mononuclear complex is provided by the alkyl substituents of the organic amide ligands, which offer enhanced solubility, electron-releasing properties, and steric protection to help saturate the uranyl(VI) coordination sphere.

Isolation of a uranyl amide by “ate” complex formation

“…The few uranyl thiolates that are known are either complexed by the chelating pyridine-2-thiolate ligand, 16,17 or by [2,6-Cl 2 C 6 H 3 S] -. 18 The stability of the latter complex was rationalised by the presence of electron withdrawing chlorides at the ortho positions, which likely minimises the reducing ability of the thiolate. 18 Addition of 6 equivalents of LiS t Bu in Et 2 O to UO 2 Cl 2 (THF) 3 in DME at -25 • C results in the formation of [Li(DME)] 2 [UO 2 (S t Bu) 4 ] (3) in 96% yield (eqn (3)).…”

“…18 The stability of the latter complex was rationalised by the presence of electron withdrawing chlorides at the ortho positions, which likely minimises the reducing ability of the thiolate. 18 Addition of 6 equivalents of LiS t Bu in Et 2 O to UO 2 Cl 2 (THF) 3 in DME at -25 • C results in the formation of [Li(DME)] 2 [UO 2 (S t Bu) 4 ] (3) in 96% yield (eqn (3)). Complex 3 exhibits a singlet at 1.75 ppm in its 1 H NMR spectrum, assignable to the t Bu methyl groups.…”

Behaviour of the uranyl (UO22+) ion in different strongly acidic media: Characterisation of UO22+ in common acids by electronic absorption spectroscopy

“…4 Since the uranium atom in UO 2 2+ is in the VI oxidation state and possesses a large size, many efforts have been made also in exploring its interesting coordination chemistry. [5][6][7][8][9][10][11][12][13][14] An effective method to study chemical speciation of the uranyl ion in aqueous solution is to apply molecular and electronic spectroscopies to it, and this has been carried out in establishing the coordination chemistry of UO 2 2+ under highly alkaline conditions. 1 Although the chemistry of UO 2 2+ has also been studied under acidic conditions, 4 the nature of interaction of the ion with an acid is not clear.…”

Versatile new uranyl(vi) dihalide complexes supported by tunable organic amide ligands

“…Our initial efforts with these systems indicate that the solubility and steric protection provided by these amides offer a distinct advantage that has enabled us to isolate the first structurally characterized example of a uranyl(VI) complex possessing unsupported thiolate ligands. 17 We are investigating further the synthetic utility of these new uranyl(VI) starting complexes.…”